This invention relates to an ultrasonic atomizer unit. More particularly it relates to the energization of a piezo-electric vibrator in such a unit so as to reduce noise or undesired signals in the circuitry as well as radiated therefrom.
In general, in an ultrasonic liquid atomizer unit for atomizing water and the like by applying an ultrasonic wave thereto, it has been found to be difficult to reduce noise potentials and radiated signals in the ultrasonic liquid atomizer unit due to the relatively high frequencies and power involved, e.g., a driving input frequency of the piezo-electric vibrator of about 1 to 2 MHz or so and a power input of at least about 10 to 30 watts is required to produce atomization of about 400 to 500 cc per hour. Further, when using water, it is difficult to utilize a metal body in the outer casing.
In the past, a piezo-electric vibrator has been fixed to a chamber base to be attached to the bottom of the atomizer container of an ultrasonic liquid atomizer device. A base plate on which the driver circuit is assembled has been mounted to the chamber base, and an annular metal plate of copper or aluminum, e.g., having a wall thickness of about 0.2 to 0.8 mm, has been arranged with an insulator to surround the circumference of the base plate. Even though radiated noise may be decreased by the use of such a surrounding metal plate, noise signals passed through the power supply line are not effectively reduced.
It is also known to use a metal casing to cover both the piezo-electric vibrator (mounted on the chamber base of an ultrasonic atomizer unit) and the driver circuit that includes a power supply circuit. In such a system, a noise filter has also been arranged in the metal casing to restrict radiated noise and noise potentials. However, such arrangements are complicated and expensive, since a symmetrical noise filter is required in the power supply line ahead of the rectifier in the power supply circuit, and the noise filter should be shielded to prevent the radiated noise from being fed to the input terminal of the noise filter in the metal casing.
The present invention provides an ultrasonic atomizer unit in which the above described disadvantages are eliminated, and both noise potentials and radiated noise are decreased by a simple construction or arrangement.
In a presently preferred embodiment of the present invention, the driving circuit for energizing the piezo-electric vibrator is separated into a power supply part and an oscillator part, and shielding the latter by a metal housing. One of the power supply lines to the oscillator extends through an aperture in the housing, while the other power supply line is connected to the metal housing. A passing capacitor is preferably included in the aperture.
The invention also contemplates use of a filter in such an oscillator circuit, together with an adjustment resistor for controlling the oscillator mounted unshielded outside the metal housing.
The invention will be more completely understood by reference to the following detailed description.